From: Andrei Borzenkov <arvidjaar@gmail.com>
To: kreijack@inwind.it, Anand Jain <anand.jain@oracle.com>
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>,
Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Subject: Re: Question: how understand the raid profile of a btrfs filesystem
Date: Wed, 25 Mar 2020 07:09:16 +0300 [thread overview]
Message-ID: <8a53cf8d-980d-8c41-e35d-c8b70db1bbdc@gmail.com> (raw)
In-Reply-To: <8977ac3d-7af6-65a7-5515-caab07983672@inwind.it>
24.03.2020 20:59, Goffredo Baroncelli пишет:
> On 3/24/20 5:55 AM, Anand Jain wrote:
>> On 3/21/20 1:56 AM, Goffredo Baroncelli wrote:
>>> Hi all,
> [..]
>>> Looking at the code it seems to me that the logic is the following
>>> (from btrfs_reduce_alloc_profile())
>>>
>>> if (allowed & BTRFS_BLOCK_GROUP_RAID6)
>>> allowed = BTRFS_BLOCK_GROUP_RAID6;
>>> else if (allowed & BTRFS_BLOCK_GROUP_RAID5)
>>> allowed = BTRFS_BLOCK_GROUP_RAID5;
>>> else if (allowed & BTRFS_BLOCK_GROUP_RAID10)
>>> allowed = BTRFS_BLOCK_GROUP_RAID10;
>>> else if (allowed & BTRFS_BLOCK_GROUP_RAID1)
>>> allowed = BTRFS_BLOCK_GROUP_RAID1;
>>> else if (allowed & BTRFS_BLOCK_GROUP_RAID0)
>>> allowed = BTRFS_BLOCK_GROUP_RAID0;
>>>
>>> flags &= ~BTRFS_BLOCK_GROUP_PROFILE_MASK;
>>>
>>> So in the case above the profile will be RAID6. And in the general if
>>> a RAID6 chunk is a filesystem, it wins !
>>
>> That's arbitrary and doesn't make sense to me, IMO mkfs should save
>> default profile in the super-block (which can be changed using ioctl)
>> and kernel can create chunks based on the default profile.
>
> I'm working on this idea (storing the target profile in super-block).
What about per-subvolume profile? This comes up every now and then, like
https://lore.kernel.org/linux-btrfs/cd82d247-5c95-18cd-a290-a911ff69613c@dirtcellar.net/
May be it could be subvolume property?
> Of
> course this increase the consistency, but
> doesn't prevent the possibility that a mixed profiles filesystem could
> happen. And in this case is the user that
> has to solve the issue.
>
> Zygo, suggested also to add a mixed profile warning to btrfs (prog). And
> I agree with him. I think that we can use
> the space info ioctl (which doesn't require root privileges).
>
> BR
> G.Baroncelli
>
>> This
>> approach also fixes chunk size inconsistency between progs and kernel
>> as reported/fixed here
>> https://patchwork.kernel.org/patch/11431405/
>>
>> Thanks, Anand
>>
>>> But I am not sure.. Moreover I expected to see also reference to DUP
>>> and/or RAID1C[34] ...
>>>
>>> Does someone have any suggestion ?
>>>
>>> BR
>>> G.Baroncelli
>>>
>>
>
>
next prev parent reply other threads:[~2020-03-25 4:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 17:56 Question: how understand the raid profile of a btrfs filesystem Goffredo Baroncelli
2020-03-21 3:29 ` Zygo Blaxell
2020-03-21 5:40 ` Andrei Borzenkov
2020-03-21 7:14 ` Zygo Blaxell
2020-03-21 9:55 ` Goffredo Baroncelli
2020-03-21 23:26 ` Zygo Blaxell
2020-03-22 8:34 ` Goffredo Baroncelli
2020-03-22 8:38 ` Goffredo Baroncelli
2020-03-22 23:49 ` Zygo Blaxell
2020-03-23 20:50 ` Goffredo Baroncelli
2020-03-23 22:48 ` Graham Cobb
2020-03-25 4:09 ` Zygo Blaxell
2020-03-25 4:30 ` Paul Jones
2020-03-26 2:51 ` Zygo Blaxell
2020-03-23 23:18 ` Zygo Blaxell
2020-03-24 4:55 ` Anand Jain
2020-03-24 17:59 ` Goffredo Baroncelli
2020-03-25 4:09 ` Andrei Borzenkov [this message]
2020-03-25 17:14 ` Goffredo Baroncelli
2020-03-26 3:10 ` Zygo Blaxell
-- strict thread matches above, loose matches on Subject: below --
2020-03-20 17:58 Goffredo Baroncelli
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